Omega Centauri in Infrared

Another beautiful image of Omega Centauri, a globular cluster (or dwarf galaxy?) in the southern sky. This image is taken by NASA’s Spitzer Space Telescope, which study the universe in infrared light, that’s why the colour looks different to the one taken by Hubble Space Telescope.

Omega Centauri by Spitzer

In this false colour view of Omega Centauri, Spitzer’s infrared observations have been combined with visible-light data from the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory in Chile. Credit: NASA/JPL-Caltech/ NOAO/AURA/NSF

This image is a combination of visible light (near the red end) and infrared light, relatively the visible light is “bluer”, thus it is represents by blue colour and the red represent the infrared data. So the “blue” stars actually are not blue, according to our eye they will look orange red.

Globular clusters are one of the oldest objects in the universe. In some cases, they can be almost as old as the universe itself. Since high-mass stars live a shorter life*, all of them in the cluster have already died by now, going supernovae and leaving behind black holes (if they were massive enough) or neutron stars. Those of medium-mass may have long blown off their outer layer and became planetary nebulae, leaving behind white dwarfs.

So what are left now are only low-mass stars, which can live up to billions of years. But most of them by now may have also evolved into red giants, puffing off their outer layers, contributing dust to the cluster. However, Spitzer found very little dust around any but the most luminous, coolest red giants, implying that the dimmer red giants do not form significant amounts of dust. The space between the stars in Omega Centauri was also found to lack dust, which means the dust is rapidly destroyed or leaves the cluster.

The red giants seen by Spitzer are the yellow and red dots in the image above. The stars that appear blue are less evolved. Red giants emit most of their light in infrared because they are cooler and because of the reddening of lights by the dust that surrounds them.

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*High-mass star needs to burn its fuel faster in order to produce enough energy to keep it from collapsing under its own huge gravity (bigger mass bigger gravity). Burn fuel faster = run out of fuel faster = die faster. The opposite goes for low-mass stars.

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~ by thChieh on April 13, 2008.

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